Known gas fuel feed systems substantially comprise a tank of liquefied-gas fuel; a pressure reducer connected fluidically to the tank to reduce the pressure of the fuel and convert it to the gaseous state; and at least one electro-injector connected fluidically at opposite ends to the pressure reducer and the engine cylinders to selectively inject gas fuel into the cylinders at predetermined times.
More specifically, each electro-injector comprises a hollow casing defining an inlet connected fluidically to the pressure reducer; and a number of outlets connected fluidically to respective engine cylinders. The casing houses a number of armatures movable, by respective electromagnets controlled by a central control unit, between a closed configuration and an open configuration, in which they respectively prevent and permit gas fuel flow from the casing through a relative outlet, and injection by a respective intake pipe into a relative cylinder.
More specifically, each armature comprises a shutter, which is selectively brought to rest on the relative outlet.
When each armature is in the closed configuration, the relative shutter is held resting on the relative outlet of the electro-injector by a spring, so as to prevent gas fuel flow to the relative intake pipe and, from there, to the relative cylinder.
When each armature is in the open configuration, the relative shutter does not interfere with the relative outlet, thus allowing gas fuel flow to the relative cylinder.
The electro-injector is fixed in a predetermined position inside the engine compartment by connecting means interposed between the casing and the engine compartment.
Given the increasing complexity of automotive internal combustion engines and, hence, “crowding” of the engine compartment, the electro-injector may sometimes have to be located relatively far away from the cylinders or, at any rate, not in the best position in terms of engine performance.
In fact, the length of each intake pipe depends on the distance between the outlet of the relative electro-injector and an inlet section of the relative cylinder, once the electro-injector is fixed inside the engine compartment.
A need is felt within the industry for electro-injectors designed to ensure fast, highly accurate gas fuel injection into the cylinders in response to a control signal supplied, for example, by pressing an accelerator pedal.
This means minimizing the length and volume of each intake pipe to reduce the fall in gas fuel injection pressure caused by load losses along the intake pipe; and reducing the delay between generation of the control signal and gas fuel injection, which is substantially caused by inertia and compressibility of the gas in each intake pipe.
A need is also felt within the industry for electro-injectors adaptable to engines of different displacements and operating parameters, without involving the electromagnet central control unit.
Finally, a need is also felt within the industry to adjust, once the electro-injector is connected to the cylinders, the time taken by the armature to return to the closed configuration after the electromagnet ceases operating.